Compound cylinder



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FFICE draullc poration of California Brake Company, Detroit. Mich., a cor- Appueauon Jury 11, 1932', sensi No. 621,784 s claims. (ci. eli-sae) My invention pertains to compound cylinders and is particularly concerned with compound cylinders especially adapted for use in power transmission systems of the fluid type.

.An object of my invention is to provide a compound cylinder having high and low pressure pistons, and means for rendering the low pressure piston ineffective upon the creation of a predetermined pressure.

Another object is to provide a compound cylinder in which there is no back pressure on the low pressure cylinder after it has been rendered ineffective.'

Another object is to provide a compound cylinder wherein the pressure at which the low pressure cylinder is rendered ineffective may be accurately predetermined.

.Another object is to provide a compound cylinder wherein the pressure at which the low pressure cylinder is rendered ineffective may be changed readily to meet the different conditions.

Another object is to provide a compound cylinder which is simple in structure, economical to manufacture, durable in use, and automatic in operation.

Another object is to provide a compound cylinder which is equally adapted for use in diilerent kinds of power transmission systems of the uid type.

Other objects and advantages will become apparent as the description proceeds.

In the drawings,

Fig. 1 is a vertical section through one embodiment of my invention;

Fig. 2 is a horizontal section taken on the line 2-2 of Fig. 1;

Fig. 3 is a diagrammatic illustration of one type of hydraulic system in which this embodiment of my invention may be incorporated;

Fig. 4 is a view similar to Fig. l, but showing a diierent embodiment of my invention;

Fig. 5 is a transverse vertical section taken on the line 5 5 of Fig. 4; land Fig. 6 is a diagrammaticillustration of a type of hydraulic system in which Vthe embodiment shown in Figs. 4 and 5 may be incorporated.

Referring to the drawings, and particularly to Figs. 1, 2, and 3, Ihave'shown one embodiment oi' my invention as having a casting i providing a chamber il which forms a fluid reservoir. The upper end of the chamber is normally closed by a removable cover I2 which is held in place by a bolt I3 threaded into a boss i4 which i'orms a part of the casting I0.

A gasket I of rubber, cork. or other suitable material. is clamped between the cover I2 and the top oi' the casting to form a huid-tight seal therebetween. The bolt I3 is provided with a. longitudinal bore i6 connecting with a transverse bore il. These two bores constitute an air vent for the reservoir Il.

The casting I0 has formed therein a large diameter low pressure cylinder i8 and a high pressure cylinder i9 of smaller diameter. In the low pressure cylinder is located a metallic piston having a forward face provided with a rubber gasket 2i which forms an effective seal with the cylinder wall during the forward or right-hand movement of the piston 20. 'I'he gasket 2l is held against the forward face oi' the piston by a return spring 22 which normally maintains the piston 20 in the position shown in Fig. 1. In this position the rear of the piston rests against a stop ring 23 which is clamped between a shoulder provided by the casting I0 and a c spring 2l.

The piston 20 has an annular recess 25 which is always maintained in free communication with the interior oi' the reservoir il by means of port 2B. 'Ihe iluid in the annular recess 25 forms a fluid seal which prevents entry of air into the active part of the cylinder during the return stroke of the piston. The Jrear oi the piston is provided with an annular rubber gasket 2l which is c-shaped in cross-section and which functions to prevent leakage of :fluid past the rear of the piston.

The piston 20 has a tapered socket 28 which receives one end oi' a piston rod 29. The piston rod 29 simply rests against the end of the socket and forms a separable abutting connection therewith. The contacting portions of the piston rod and socket are made hemispherical to provide for misalignment of the piston rod and piston without resulting cooking of the piston in the cylinder bore. The left-hand end of the piston rod is yoke-shaped, as indicated at 30, and is `pivotally connected to an' operating lever 3| which may be operated either manually or by power. A flexible rubber boot 3| is commonly provided to protect the end of the low pressure cylinder against the entry of dirt and moisture.

A small port 32 connects the reservoir il with that part of the cylinder I8 in front of the gasket 2i when` the piston and gasket are in their retracted position, es shown in the drawings. The

piston 20 and gasket 2| are preferably provided with grooves 33 and 34, respectively, to facilitate the iiow of fluid past the piston and ing the return stroke of these parts. A forwardly Y extending ringer 35 is threadedly attached t'o the gasket durpiston 26 for a purpose to be hereinafter described.

In the high pressure cylinder I9 is located a metallic piston 36 having a cup-shaped gasket 31 of rubber or other suitable material. The gasket 31 is held against t-he forward face of the piston 36 by return spring 38 which also normally holds the piston 36 against the annular stop member 39 which is held against the shoulder formed at the junction between the high and low pressure cylinders by the spring 22 which is of greater strength than the spring 38.

The piston 36 has a rounded socket 40 for receiving the rounded end of the finger 35. The socket 4I) is connected by means of passageway 4I with an annular groove 42 which in turn communicates with bore 43 leading to a valve chamber 44. Bore 43 also communicates with port 45 which leads to that part of the high pressure cylinder immediately in front of the cup-shaped `gasket 31 when the piston and cup-shaped gasket are in retracted position.

The upper end of the valve chamber 44 is closed by a threaded plug 46 having a ball valve 41 pressed by a spring 48 against a valve seat formed in the lower end of the plug 46. The spring is held in place by a retainer 49 which is attached to the plug 46 by bending the lip 5U over the outer edge of the lateral flange formed by the lower end of the retainer 49.

The valve 41 controls a passageway extending through the plug 46 and leading back to the reservoir II. The size of the opening through the valve seat and the strength of the spring 48 are so proportioned that the valve 46 will open under a predetermined pressure. By simply unscrewing the plug 46 and replacing it by another, having a valve set to open at a higher or lower pressure, it is possible to adapt my compound cylinder for differentpurposes and for uses under widely varying conditions.

A piston valve 5I is located in the valve chamber 44 and has a reduced cylindrical portion 52 of diameter considerably smaller than the diameter of the valve chamber 44. The piston valve 5I has octagonal ends 53 and 54 which guide the piston valve in the valve chamber but permit flow of fluid therepast. The upper or left-hand end of the piston valve 5I has a projection 55 of smaller diameter than the passageway through the seat for the valve 41, and when the piston valve 5I is moved to its upper or left-hand position, as will be hereinafter described, the projection holds the ball valve 41 away from its seat while permitting iiuid to flow from the valve chamber back into the reservoir.

A rubber cup washer or gasket 56 is associated with the lower or right-hand end of the piston valve 5I, and this cup washer is provided with grooves 51 to facilitate flow of fluid past the cup washer and into passageway 58 which communi:- cates with the forward end of the high pressure cylinder I9. A metal clip 59 acts as a stop to limit movement of the piston valve 5I and rubber cup washer 56 in one direction.

The right-hand or outlet end of the high pressure cylinder is closed by a tubular member 68 which is threadedly engaged therewith, and a suitable gasket 6I is clamped between the end of the casting I0 and the tubular member 66 to provide a fluid-tight seal. A shoulder 62 is formed in the tubular member 68 and a rubber washer 63 is located against this shoulder and forms the valve seat part of the two-way valve mechanism indicated generally by reference numeral 64. This valve mechanism may be of any desired type but is herein shown as being of the kind described and claimed in my copending application for United States Letters Patent, Serial No. 472,666, filed August 2, 1930.

In Fig. 3 I have indicated a form of installation in which the pipe line 65 leads to motor cylinders 66 having pistons 61 for reciprocating piston rods 66 connected with any suitable type of mechanism whichv is actuated by the power thus transmitted by the fluid system. In the particular type of system illustrated in Fig. 3, I have shown a bleed conduit 69 leading back from one of the motor cylinders 66 to a return connection 10 formed in a boss 1I constituting part of the casting I0 and located at the upper right-hand side of the reservoir I I. The return connection 10 can communicate with the interior of the reservoir I I by means of an L-shaped passageway 12. In normal operation of the system shown in Fig. 3, this passageway 12 is closed by the tapered inner end of a bleed screw 13, so that the fluid surges back and forth through the pipe line 65 between the compound cylinder and the motor cylinders 66.

In originally filling the system with fluid, or whenever it is desirable to remove air which may have found its way into the pipe line 65 and motor cylinders 66, the bleed screw 13 may be unscrewed sufficiently to open the passageway 12 and the compound cylinder operated to force fluid into the end of the pipe line 65. 'I'his operation is continued until all air in the pipe line 65 and motor cylinders 66 has been forced therefrom and forced through the pipe 69 to the reservoir I I, whence this air may escape to atmosphere through vent passageways I6 and I1. As soon as all air has thus been bled from the system, the bleed screw 13 is again screwed into normal position with its tapered end closing the L- shaped passageway 12.

The operation of this embodiment of my invention is as follows. With the parts in the position shown in Fig. 1, actuation of the lever 3l will advance piston 20 and gasket 2I so that the gasket closes port 32 leading from low pressure cylinder I8 back to reservoir II. Thereafter continued advance of the piston 2D forces fluid through recess 4D, port 4I, annular groove 42, bore 43, into valve chamber 44. The fluid forced into valve chamber 44 flows past the piston valve 5I and cup washer 56 into passageway 58 and thence into the right-hand or outlet end of the high pressure cylinder. Here the fluid flows through valve 64 and into pipe line 65. This discharge of fluid into the pipe line raises the pressure of the fluid in the pipe line 65, motor cylinder 66 and in the operating parts of the compound cylinder.

When this pressure reaches a predetermined Value, ball valve 41 opens and permits fluid forced into the valve chamber 44 by the low pressure piston to flow back into reservoir I I, thereby rendering the loW pressure cylinder ineffective.

Very shortly after valve 41 opens, the righthand end of finger 35 engages and advances high pressure piston 36, thereby closing port 45 and discharging additional fluid from the high pressure cylinder. The fluid discharged from the high pressure cylinder acts on cup washer 56 and piston valve 5I to move them upwardly or toward the left and bring projection 55 into engagement with ball valve 41. Cup washer 56 will not permit fluid to flow from the high pressure cylinder therepast, and thereafter the pressure created by the high pressure piston holds valve 41 open,

thus permitting fluid to flow sure cylinder back into from the low presthe reservoir without rey sure piston.

Upon release ot lever 9|, springs 22 low pressure pistons to the positions shown in Fig. 1. Usually an additional spring or similar means is provided to return the lever 3| and piston rod 29to normal position independently of the return of the pistons. l

Pistons 20 and 86 usually return faster than motor cylinder pistons 61, and under these conditions iluid from annular space 25 bypasses the right-hand end ot low pressure piston 20 and gasket 2|, such by-passing being facilitated by grooves 33 and I4. At the same time fluid can by-pass the high pressure cylinder I6 by passing around through bore Il, valve chamber 44, and passageway 56.

The fluid returned to the compound cylinder .1y the return movement of the motor cylinder pistons 61 forces valve mechanism 64 away from seat 63, and the excess iiuid in the high and low pressure cylinders is returned to the reservoir by way o1' port 46. bore 48, annular space l2, passageway 4l. and port 92.

In Fig. 3 I have illustrated the embodiment of my compound cylinder shown most clearly in pressure from the actuating Figs. 1 and 2, as being incorporated'in a iluid system of power transmission which includes a return line 69 leading directly from one of the motor cylinders to the reservoir. This return line 69 is to be understood as merely an optional and convenient means of bleeding the system and is not necessary to the successfuloperation of this embodiment 'of my invention. In fact, this embodiment oi my invention is designed for a pulsating type of fluid system in which the fluid surges back and forth in a single conduit or conduit system and is especially designed for use with present forms oi hydraulically actuated vehicle brakes and other types oi fluid transmission systems in which it is not common and frequently impossible to provide a special return line to the reservoir which would correspond to conduit 69.

Where this form of my invention is used in the hydraulic brake systems of the type now in common use, the system would be bled by means ci the bleeder screws now commonly associated with the motor cylinders located at the vehicle wheels. Where my invention is to be used in such systems, the return connection 10, passageway 12, andfbleed screw 13, could be eliminated.

That form of my invention shown in Figs. 4, 5, and 6 ls generally the same as that previously described. This form of my invention, however, is especially designed for incorporation in a circulating system in which one conduit or conduit system is utilized to connect the motor cylinders with the discharge port of my compound com pression cylinder, and a separate conduit or conduit system `is utilized to transfer iluld discharged from the motor cylinders back to the iluld reservoir associated with my compression cylinder.

In this embodiment of my invention. as shown most clearly in Figs. 4 and 5, I provide a casting 80 having a reservoir 8| which is normally closed by a removable cover 82 held in place by a bolt 89 which is provided with an atmospheric vent 04. In order to prevent undue splashing of iluid in the reservoir, I preferably provide a cork disk and 80 return the high and fluid to flow i'rom |2| which floats on the surface oi the duid in the reservoir..

The casting 80 also provides a low pressure cylinder 86 and a high pressure cylinder 86; A piston BHs located in the low pressure cylinder and is actuated by a piston rod 88 connected to a suitable actuating lever 89 which may be manually or powerroperated by any suitable means.' The piston 81 has anannular recess 90 maintained in communication with the reservoir 8| by port 9|. The duid which fills this recess 90 acts as a fluid seal toprevent leakage of air past the rear oi' the piston. An annular rubber sealing gasket 92 prevents escapel of liquid from the recess 9u past the rear of the piston and also cooperates with the fluid seal in preventing leakage of air past the piston during its return stroke.

Rearward movement of the piston 81 is limited y Ithe upper end of a removable drain plug 93. A rubber gasket 94 is pressed against the forward face of the piston 81 by return spring 95; Piston 81 and gasket 94 are cup-washer or gasket a return spring |0|. Rearward or return move-y ment oi the high pressure piston is limited by the annular stop member |02 held in place by the spring 95 which is of greater strength than the spring lili. The high pressure piston 99 has openings |03 and annular groove |04 for establishing communication between the low pressure cylinderand bore leading to valve chamber |06. The upper end of the valve chamber is closed by a removable plug |01 carrying a ball valve |08 set to release at a predetermined pressure.

The valve` chamber contains a piston valve |09 having a projection ||0 for holding open the ball valve |06 while the low pressure cylinder is ineiective. The piston valve |09 is provided with a rubber gasket which seals in one direction only and which, in the present instance, is shown as provided with a centrally located forward projection which serves as a limit stop. A passageway ||2 connects the valve chamber |06 with the forward end of the high pressure cylinder 86.

The outlet or right-hand end of the high pressure cylinder is closed by a. screw plug ||3 con-l taining a ball check valve ||4 which permits the high pressure cylinder into a pipe line H5, but prevents return ilow of fluid from the pipeline to the high pressure cylinder.

In the particular hook-up illustrated in Fig. 6, pipe line ||5 leads to motor cylinders l I6 havlng pistons H1 i'or actuating piston rods I8 connected to any suitable mechanism. Since check valve Ill prevents the return of iiuid from the motor cylinders I6 by way of conduit H5, a separate conduit H9 ls provided to return the uid from the motor cylinders to the iiuid reservoir.

' Conduit H9 is normally closed by relief valve |25. This relief valve includes a valve member |26 which is normally held by spring |21 in sealing engagement with the adjacent end of one of the pipes forming the conduit I I9. The spring |21 may be of such strength that the valve mem- 'lber |26 will be automatically moved to open poisition when the pressure in the motor cylinders reaches a predetermined maximum, but in the ordinary use of the mechanism the relief valve is opened by exerting a pressure on lever |22 in the direction indicated by the arrow. Ihis pressure may be exerted manually or by any suitable means and, in at least one usage of my invention, this pressure is preferably exerted by the return movement of the lever I! or other means for operating the compound cylinder.

Where the reservoir is located below the motor cylinders and it is desired to maintain the motor cylinders and pipe lines iull oi uid, or where for any reason it is desired to maintain a pressure on the fluid in the pipe lines and motor cylinders, a spring pressed check-valve |2B may be provided. This check valve ordinarily operates under very light spring tension but may be given any spring tension desired. In most installations the reservoir can be located above the motor cylinders and the check valve |20 eliminated entirely.

In this latter embodiment of my invention I have shown the casting 8U as provided with one or more bosses |22 for receiving the threaded ends oi. attaching bolts |23 by means oi which my compound cylinder and reservoir unit may bc attached to a suitable support such as that indicated at |24.

Having thus described my invention, what I .claim is new and desire secure by United States Letters Patent is:

l. In mechanism of the class described, the combination o! a reservoir, a low pressure cylinder, a piston reciprocable therein, means for reciprocating said piston, a forwardly extending projection carried by said piston, a high pressure cylinder, a piston reciprocable therein, said piston being normally spaced from said projection but being adapted for movement thereby, a discharge conduit connected to said high pressure cylinder, a passageway by-passing said high pressure piston, a chamber intercepting the passageway, a valve in said chamber permitting ilow through the passageway in one direction only a loaded valve connecting said passageway with said reservoir, and passageways in the high pressure piston providing a communication between the by-pass and the low pressure cylinder.

2. In mechanism of the class described, the

combination of a reservoir, a low pressure cylinder. a piston reclprocable therein, means for reciprocating said piston, a high pressure cylinder, a piston reciprocable in the high pressure cylinder, means carried by the piston in the low pressure cylinder for actuating the piston in the high pressure cylinder after an initial movement of the piston in the low pressure cylinder, a valve chamber spaced laterally from said high pressure cylinder, a piston valve in said chamber, said piston valve by-passing' fluid in one direction only, a passageway connecting said chamber with each of said cylinders. a loaded valve in said chamber controlling communication between said chamber and said reservoir, a piston valve operable for holding said loaded valve in open position during the compression stroke of the piston in the high pressure cylinder, and valve means at the outlet end of said high pressure cylinder.

3. In a cylinder and reservoir unit of the class described, the combination of a reservoir, a low pressure cylinder supplied therefrom, a high pressure cylinder adapted to receive duid discharged from said low pressure cylinder, a piston in said low pressure cylinder, a piston in said high pressurecylinder, a port normally connecting said low pressure cylinder with said reservoir, a port normally connecting said high pressure cylinder for two-way communication with said low pressure cylinder, means for advancing said pistons to close said ports, a passageway connecting said cylinders for one-way communication only, a chamber intercepting the passageway and communicating with the reservoir, and a loaded valve in said chamber controlling the communication.

ERWIN F. LOWEKE. 

